Major progress has been achieved in developing and optimizing HER2-targeted therapies for breast cancer. Examples of FDA-approved drugs with significant clinical efficacy for metastatic disease include the anti-HER2 antibody trastuzumab, the dual EGFR-HER2 kinase inhibitor lapatinib, the anti-HER2-HER3 dimerization inhibitor pertuzumab, and the antibody-drug conjugate T-DM1 (Krop, I. E., et al. Lancet Oncol (2014); Slamon, D. J., et al. The New England journal of medicine 344, 783-792 (2001)). Clinical data reveal an increased incidence of brain metastases (BM) after adjuvant trastuzumab therapy (Olson, E. M., et al. Annals of oncology: official journal of the European Society for Medical Oncology/ESMO 24, 1526-1533 (2013). This incidence is high as 50% in patients with advanced disease. Established BM often exhibit resistance to trastuzumab, a phenomenon which has been mostly attributed to inadequate penetration of the antibody through the blood-brain barrier (BBB) (Lampson, L. A. mAbs 3, 153-160 (2011). However, despite adequate drug delivery, the efficacy of small molecules on BM is also very limited and can only be marginally increased through the addition of further therapeutic modalities (Lin, N. U., et al. Journal of clinical oncology 26, 1993-1999 (2008); Lin, N. U., et al. Clinical cancer research: an official journal of the American Association for Cancer Research 15, 1452-1459 (2009); Bachelot, T., et al. The lancet oncology 14, 64-71 (2013)). Brain metastases is a devastating progression of breast cancer. Treatment options are limited, and the same anti-HER2 therapies that slow growth systemically do not typically control brain metastases. Thus, there is a need to identify a drug(s) that can be useful for treating breast cancer brain metastases.